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Alloy bridge piece repaired in situ.


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After 50 years my MK1 Vitesse has suffered the usual stripping of the threads in the engine block front alloy bridge piece. It has one forward facing hole for the timing chain cover and two underneath for the sump and all three had lost their 5/16" UNF threads resulting in substantial oil leaks. Well I can now confirm that its possible to retap all of them M10 without removing the bridge piece or engine although access in situ isnt good.

The sump holes are the easiest and if completely stripped can be tapped directly as the hole size is perfect otherwise they should be drilled out to 8mm. However note that the other end of the hole is open so aluminium swarf could go into the sump and its best to procede slowly and allow any debris to fall back out of the holes.

The front hole is more difficult as the radiator and crank pulley have to be removed but then it too can be done taking great care to get the tap aligned correctly. This hole is blind so theres no swarf risk but obviously can only be drilled/tapped to a certain point - I only went far enough to allow the new bolt to fully enter as the casting is relatively thin in this area.

The replacement M10 x 20mm bolts must be allen socket cap heads as only these have heads small enough to fit in the flanges of the sump and timing cover but this thread is much more substantial so allows the joints to be fully tightened without risk. Finally I used spring washers on all the bolts plus PTFE tape on the sump ones to stop any oil seeping down the threads from the open ends in the sump.

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yes Im quite pleased as Ive saved the cost of a new steel bridge piece (not much point getting another ally one) and all the hassle of changing it. And with M10 Allen bolts I cant see much chance of anyone mixing them up with the original bolts🤗

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